On a Variety of Glaucophane from the Val Chisone (Cottian Alps)

Extract

As I was descending the Val Chisone from the Col de Sestriéres last summer, my eye was attracted by the peculiar colour of an erratic, which was lying on the hillside very near the road. The violet-blue tint, generally indicating the presence of giaucophane, was perceptible, especially in certain lights, but, as it was much less strongly marked than in rocks in which I had previously observed the mineral, I felt doubtful. However, I secured a good specimen, and now find on microscopic examination that glaucophane is present, though it is a pale coloured variety, differing from those which I have hitherto examined.

The block was a fairly large one, perhaps more than a square yard in area, and a couple of feet thick. I did not, however, take measurements, as the exact size was unimportant.